The subsequent development of multiple primary malignancies in patients with squamous cell carcinoma of the head and neck is well documented. Especially in the upper aerodigestive tract, Slaughter et al. explained this phenomenon with the concept of ""field cancerization"". So entire upper aerodigestive tract must be evaluated thoroughly at the time of initial tumor evaluation and during follow up period. We analyzed 44 patients with multiple primary tumors among the patients between 1966 and 1988 retrospectively. The above cases were grouped into group I, in which subsequent tumors were found in the upper aerodigestive tract and group II, in which other than the head and neck. The results are as followings ; 1) In group I, larynx cancers were associated with lung cancers and cancers of oral cavity and hypopharynx were with esophageal cancers. In group II, there was no remarkable relationship between tumor sites. 2) Overall, 2nd primary tumors were found in the order of esophagus, oral cavity, lung, and hypopharynx. In the nasopharynx tumors, 9 out of 10 cases, subsequent tumors were found in the head and neck contradictory to the past reports. 3) The synchronous tumors were 40% in group I, and 55% in group II. 4) Important clues to the 2nd primary tumors were new complaints of patient during follow up period. The importance of regular follow up check was appreciated. 5) The diagnostic tools of panendoscopy(laryngoscopy, esophagoscopy, and bronchoscopy) and esophagogram were effective. 6) Many cases of mortality were due to 2nd primary tumors, and almost within 48 months.